var nav_1 = document.getElementById("nav_1");
var nav_2 = document.getElementById("nav_2");
var nav_3 = document.getElementById("nav_3");
var nav_4 = document.getElementById("nav_4");
var box1 = document.getElementById("box1");
var box2 = document.getElementById("box2");
var box3 = document.getElementById("box3");
var box4 = document.getElementById("box4");
var menu1 = document.getElementById("menu1");
var menu2 = document.getElementById("menu2");
var menu3 = document.getElementById("menu3");
var menu4 = document.getElementById("menu4");
var menua1 = document.getElementById("menua1");
var menua2 = document.getElementById("menua2");
var menua3 = document.getElementById("menua3");
var menua4 = document.getElementById("menua4");

nav_1.onclick=function(){
	box1.style.display="block";
	box2.style.display="none";
	box3.style.display="none";
	nav_1.className="nav11";
	nav_2.className="nav22";
	nav_3.className="nav22";
	menu1.className="dis";
	menu2.className="undis";
	menu3.className="undis";
	menua1.className="dis";
	menua2.className="undis";
	menua3.className="undis";
	box4.style.display="none";
	menua4.className="undis";
	menu4.className="undis";
	nav_4.className="nav22";
	}
nav_2.onclick=function(){
	box1.style.display="none";
	box2.style.display="block";
	box3.style.display="none";
	nav_1.className="nav12";
	nav_2.className="nav21";
	nav_3.className="nav22"; 
	menu1.className="undis";
	menu2.className="dis";
	menu3.className="undis";
	menua1.className="undis";
	menua2.className="dis";
	menua3.className="undis";
	box4.style.display="none";
	menua4.className="undis";
	menu4.className="undis";
	nav_4.className="nav22";
	}
nav_3.onclick=function(){
	box1.style.display="none";
	box2.style.display="none";
	box3.style.display="block";
	nav_1.className="nav12";
	nav_2.className="nav22";
	nav_3.className="nav21"; 
	menu1.className="undis";
	menu2.className="undis";
	menu3.className="dis";
	menua1.className="undis";
	menua2.className="undis";
	menua3.className="dis";
	box4.style.display="none";
	menua4.className="undis";
	menu4.className="undis";
	nav_4.className="nav22";
	}	
nav_4.onclick=function(){
	box1.style.display="none";
	box2.style.display="none";
	box3.style.display="none";
	box4.style.display="block";
	nav_1.className="nav12";
	nav_2.className="nav22";
	nav_3.className="nav22"; 
	nav_4.className="nav21"; 
	menu1.className="undis";
	menu2.className="undis";
	menu3.className="undis";
	menu4.className="dis";
	menua1.className="undis";
	menua2.className="undis";
	menua3.className="undis";
	menua4.className="dis";
	}